Monophasic samples of seven different oxides with perovskite structure, and also gamma-NaAlO2 have been prepared for catalytic applications. They have been characterized by X-ray diffraction and electron microscopy, then by X-ray photoelectron spectroscopy (XPS). The XPS spectra of LaAlO3, La0.9Sr0.8Al0.8Cu0.1Ru0.1O3, La0.8Sr0.2Al0.8Cu0.1Ru0.1O3 and gamma-NaAlO2 contained only one well-defined O 1s peak. The binding energy obtained from the oxygen peak of the perovskites (529.8 eV) was, however, significantly different from that of gamma-NaAlO2 (532.2 eV). The other perovskite oxides, La0.9Ca0.1AlO3, La0.8Ca0.2AlO3, La0.8Sr0.2AlO3 and LaAl0.8Cu0.2O3 had two more or less well-resolved O 1s peaks separated by 2.4 eV. Tentatively, we have interpreted these observations to mean that, in the latter compounds, the surface is reconstructed so that the Al3+ ions have changed their coordination from octahedral to tetrahedral.